The Diabetes Prevention Trial 1 (DPT-1) is a national, multi-center trial to screen a large cohort of first-degree relatives of patients with insulin-dependent diabetes mellitus (IDDM) for the presence of markers of risk for diabetes. Those relatives who prove to be at high risk for the development of IDDM will be asked to participate in a randomized open trial to determine whether early insulin treatment can delay/ prevent the onset of IDDM compared to untreated controls. The present application is for the screening and staging portions of this project, but not the intervention portion of the trial.